Microwave tube construction



Oct 8, 1963 L. J. BRADY 3,106,659

MICROWAVE TUBE CONSTRUCTION Filed March 24, 1959 2 Sheets-Sheet l Ly/vuJ BRADY INVENTOR.

Oct. 8, 1963 L, J. 86AM 3,106,659

MICROWAVE TUBE CONSTRUCTION Filed March 24, 1959 2 Sheets-Sheet 2 EggLyA/A/ $3840) INVENTOR.

United States Patent York Filed Mar. 24, 1959, Ser. No. 801,536 2Claims. (Cl. 313-84) This invention generally relates to improvements inelectron tube constructions and more particularly to improved ferritemagnet field focusing assemblies particularly useful for microwaveelectron tubes or the like.

In the transmission and amplification of extremely high frequencyelectromagnetic waves in the microwave region, the use of microwaveelectron tubes have found great acceptance. In such devices streams ofelectrons are directed within a tube in various paths and focused andcontrolled by permanent magnet assemblies external to the tube andgenerating strong magnetic focusing fields through the tube to interactwith the electron flow. The development of larger capacity tubes tohandle increased microwave power has required the use of larger andbulkier magnetic focusing means to satisfy the need for strongermagnetic fields; and despite the improvement brought about by the recentintroduction of ferrite permanent magnets for such applications, therestill exists a great need for reducing the size and weight of themagnetc field producing and transfer structure, or in other words,obtaining the required magnetic field strength while reducing the sizeand weight of the magnetic generating means, and the means fortransferring the magnetic lines of force from the ferrite magnets.

According to the present invention there is provided an improvedpermanent magnet flux generating and focusing means which by actualmeasurement produces and transfers from to more useful magnetic flux forsuch applications than prior devices of the same overall weight andvolume. This substantial improvement is brought about by stacking orcascading a plurality of permanent magnet ferrite rings through improvedmagnetic coupling and focusing means in such manner as to markedlyreduce the leakage flux normally pro duced and thereby to focus andstrengthen the useful flux being directed through the tube.

It is accordingly a primary object of the present invention to providean improved ferrite permanent magnet focusing structure capable ofproducing greater useful flux with no increase in size or weight of thefocusing means.

A further object is to provide a multiple array of ferrite permanentmagnets having improved means for intercoupling the magnets to minimizeleakage flux and concentrate and strengthen the useful flux generatedand transferred thereby.

Other objects and many attendant advantages will be more readilycomprehended by those skilled in the art after a detailed considerationof the following specification and drawings wherein:

FIG. 1 is a perspective view depicting one ferrite permanent magnet andpreferred coupling means therefor, shown in exploded relation;

FIG. 2 is a cross-sectional view of one half of the magnet and couplingmembers through line 22 of FIG. 1;

FIG. 3 is a transverse cross-section depicting a plurality of thecoupled rings of FIG. 1 in a cascaded array;

FIG. 4 illustrates the preferred coupling member in plan view and incross-section, arranged side-by-side; and

FIG. 5 is an enlarged cross-sectional view, similar to FIG. 2 forillustrating the flux pattern produced.

Referring now to the drawings for a detailed con- 3,106,659 PatentedOct. 8, 1963 sideration of one preferred embodiment of the invention,there is shown in FIG. 1 a ferrite permanent magnet ring 10 having acentral opening 11 and being formed with its north pole on theright-hand side thereof, as shown, and its south pole at its left-handsurface (not exposed). Positioned at the right-hand side of magnet 10 isa first generally ring shaped coupling member 12 of magneticallysusceptible material, and positioned adjacent the left-hand side is asecond identical coupling member 13, with both members in coaxialalignment with the central axis of magnet 10 to sandwich the magnet asshown in FIG. 2.

The left and right-hand coupling members 12 and 13 are provided with hubportions 15 projecting inside magnet opening 11 to define a smallerdiameter opening 14 therein.

The function of coupling members 12 and 13 is to provide a lowreluctance magnetic flux path from the magnet right-hand surface (northpole) to the magnet left-hand surface (south pole) through the centralopening 11 of the magnet and do so in such manner as to focus a strongmagnetic flux through this central aperture 14 through the couplingmember and thence through an electron tube or the like (not shown) whichmay be accommodated within the opening 14.

As best shown by FIGS. 2, 4, and 5 these inwardly projecting hubportions 15 on each coupling ring are raised or thickened to form a wideinner rim surface 16 peripherally defining the central opening therein,and in cross-section having the shape of a wedge or pedestal with thewide rim surface or base thereof 16 positioned coaxially with and remotefrom the inner edge surface of magnet ring Iii. From the base surface 16the edges 17, 17a of the hubs are transferred inwardly along sides 18 asthey approach the magnet 10, as shown.

As thus constructed, the coupling member 12 provides a low reluctanceflux path from the north pole right-hand of magnet 10 to an enlarged rimarea 16 positioned remote from the magnet and within the centralaperture thereof, and the left-hand coupling member likewise provides asimilar low reluctance flux path from the south pole left-hand of themagnet to a simialr enlarged rim area 16a in closely spaced side-by-sidealignment with rim area 16 whereby a strong magnet flux 19 may beproduced between these rim areas 16 and 16a inside the central aperature14, as best shown by FIG. 5.

However, since the sides 18 and 18a of the projecting hubs are also inconfronting relation a certain amount of undesired leakage flux 20 isalso produced between these sides, which for purposes of the presentinvention is not gainfully employed for a useful purpose. Accordingly,these sides 17 and 17a are deliberately transferred in a direction awayfrom each other as they approach the edge ofmagnet 10 to provide aprogressively increasing reluctance path to the passage of leakage flux,thereby minimizing the amount of leakage flux 20 which passes betweenthese sides. The eifect of reducing this leakage flux 20 is tostrengthen and concentrate the useful magnet flux being produced betweenrim areas 16 and 16a; and actual measurement has shown that this usefulflux may be increased in the order of from 5 to 10% over that otherwisebeing generated between these areas.

Thus the novel construction and interaction of the coupling members 12and 13 and magnet ring 10 focus a concentrated useful magnetic field ina direction predominantly transverse to the magnet ring, that is from 5to 10% greater than that otherwise obtainable from a ferrite magnet ofthe same size and weight. Stated in another manner the magnet andcoupling member construction of the present invention enables areduction in the size and weight of these members to be obtained whileproducing a magnetic field of given intensity.

To provide an elongated magnetic field of this type to encircle the longneck portions of a microwave or other electron tube for focusingpurposes, a plurality of these ferrite permanent magnets and couplingmembers therefor may be cascaded or stacked in the manner shown by FIG.3. As shown each of the ring magnets are disposed in axial alignment,with a coupling member, as described above, being intermediate each pairof magnet rings and also in axial alignment therewith, thereby toprovide an elongated magnetic field transversely through the centralopenings of the magnets and coupling members in the direction asindicated by the arrowed line 21 entitled Flux.

What is claimed is:

1. In a ferrite magnet focusing assembly for microwave tubes, aplurality of ferrite ring permanent magnets in cascaded relation withtheir central openings in axial alignment to accommodate an electronpassage means, and means for concentrating and focusing the fiuxgenerated thereby in an axial direction through said aligned openings,said means consisting of a plurality of magnetic separating members, onemember being intermediate each pair of ferrite rings and each beingformed with a smaller diameter central opening than said magnet andhaving an elongated and symmetrical wedge shaped portion symmetrical incross section defining said smaller diameter opening, thereby to focus astrong magnetic field axially along said opening, each of saidwedgeshaped portions extending over a portion of the project ing widthof the tubular central section surrounding the smaller diameter openingof each magnetic separating member, each of said magnetic separatingmembers having a shoulder integral with each side thereof, each of saidshoulders being located radially near the wedgeshaped portion of themagnetic separating member, the ferrite rings extending outward from theshoulders of the magnetic separating members.

2. In a device of the class described, a plurality of ring shapedferrite permanent magnets in cascaded array, a ring shaped magneticallysusceptible member intermediate each pair of magnets, the magneticallysusceptible members on each side thereof providing a low reluctance pathfrom one pole of the ring magnet to an enlarged annular area within thering opening and coaxial therewith, with said enlarged areas being inside by side relationship and the edges thereof being closely spacedtogether, the portions of each magnetically susceptible member adjoiningsaid area being progressively recessed away from the confrontingportions of the other in a direction toward the magnet thereby toprovide a progressively increasing reluctance path between saidconfronting portions, whereby in cross section each said magneticallysusceptible member is in the form of a symmetrical T-shaped pedestalhaving a flat enlarged base and inwardly tapered sides thereby tominimize leakage flux, the recessed portion of each T-shaped pedestalextending over a portion of the projecting width of the base of thepedestal, each of said magnetically susceptible members having ashoulder integral with each side thereof, each of said shoulders beinglocated radially near the T-shaped pedestal, the ring opening througheach of said ring-shaped permanent magnets being fitted to a pair ofsaid shoulders, each ring-shaped permanent magnet extending outward froma pair of shoulders of adjoining magnetically susceptible members, andsaid ring permanent magnets and ring shaped magnetically suseptiblemembers having mating sides and edges interfitting with one another inaligned coaxial array thereby to provide a unitary assembly of minimumWeight and volume.

References Cited in the file of this patent UNITED STATES PATENTS2,843,775 Yasuda July 15, 1958 2,847,607 Pierce Aug. 12, 1958 2,875,273Bailey Feb. 24, 1959 2,876,373 Veith et a1 Mar. 3, 1959 2,882,439 Nishioet al Apr. 14, 1959 2,895,066 Yasuda July 15, 1959 2,911,554 Kompfner etal Nov. 3, 1959 2,945,153 Chang July 12, 1960 2,956,200 Bates Oct. 11,1960 2,965,782 Weaver Dec. 20, 1960

1. IN A FERRITE MAGNET FOCUSING ASSEMBLY FOR MICROWAVE TUBES, APLURALITY OF FERRITE RING PERMANENT MAGNETS IS CASCADED RELATION WITHTHEIR CENTRAL OPENINGS IN AXIAL ALIGNMENT TO ACCOMMODATE AN ELETRONPASSAGE MEANS, AND MEANS FOR CONCENTRATING AND FOCUSING THE FLUXGENERATED THEREBY IN AN AXIAL DIRECTION THROUGH SAID ALIGNED OPENINGS,SAID MEANS CONSISTING OF A PLURALITY OF MAGNETIC SEPARATING MEMBERS, ONEMEMBER BEING INTERMEDIATE EACH PAIR OF FERRIER RINGS AND EACH BEINGFORMED WITH A SMALLER DIAMETER CENTRAL OPENINGS THAN SAID MAGNET ANDHAVING AN ELONGATED AND SYMMETRICAL WEDGE SHAPED PORTION SYMMERTICAL INCROSS SECTION DEFINING SAID SMALLER DIAMETER OPENING, THEREBY TO FOCUS ASTRONG MAGNETIC FIELD AXIALLY ALONG SAID OPENING, EACH OF SAIDWEDGESHAPED PORTIONS EXTENDING OVER A PORTION OF THE PROJECTING WIDTH OFTHE TUBULAR CENTRAL SECTION SURROUNDING THE SMALLER DIAMETER OPENING OFEACH MAGNETIC SEPARATING MEMBER, EACH OF SAID MAGNETIC SEPARATINGMEMBERS HAVING A SHOULDER INTEGRAL WITH EACH SIDE THEREOF, EACH OF SAIDSHOULDER BEING LOCATED RADIALLY NEAR THE WEDGESHAPED PORTION OF THEMAGNETIC SEPARATING MEMBER, THE FERRITE RINGS EXTENDING OUTWARD FROM THESHOULDERS OF THE MAGNETIC SEPARATING MEMBERS.